1. Field of the Invention
The present invention relates to an image pickup apparatus including an image pickup system disposed at a rear of an objective optical system.
2. Description of the Related Art
In recent years, industrial and medical endoscopes have been widely used. In particular, there are endoscopes including an image pickup apparatus using a solid image pickup device such as a CCD arranged at a distal end of an insertion portion thereof. The insertion portion in which the image pickup apparatus is arranged is inserted into, for example, a body cavity in the case of a medical endoscope, enabling an image of a site to be examined in the body cavity to be observed via a monitor.
As disclosed in Japanese Patent Application Laid-Open Publication No. 2008-307293, in order to achieve downsizing and enhancement in assemblability, in an image pickup apparatus incorporated in a distal end portion of such endoscope, an image pickup device package is disposed at a rear of an objective optical system including a group of lenses. The image pickup device package is formed by packaging a solid image pickup device, a cover glass that protects an image pickup surface of the solid image pickup device and a circuit substrate with electronic components mounted thereon on a rear face opposite to the image pickup surface of the solid image pickup device by means of sealing using a resin.
In general, a group of lenses included in an objective optical system in an image pickup apparatus are held using a lens frame. In such lens frame-used lens holding structure, the group of lenses may be held by a plurality of lens frames, and in such case, in order to accurately hold optical positions of the respective lenses to ensure optical performance, a lens holding structure such as illustrated in FIG. 5 is often provided to dispose an image pickup device package at the rear of the lens holding structure.
In the lens holding structure illustrated in FIG. 5, a first lens frame 210 holding one lens 200 included in an objective lens group is joined to a second lens frame 211 holding the other lens 201 by making the second lens frame 211 butt an inner portion of the first lens frame 210, whereby the lenses 200 and 201 are disposed at prescribed positions in an optical axis direction, and an image pickup frame 212 holding a non-illustrated image pickup device package is joined to the second lens frame 211.